Keep to the Code:
Translucent Curtainwalls Can Take What’s Thrown & Look Good Doing It
Judy Mann,
Posted
09/01/2008
Translucent
curtainwalls can meet demanding code requirements while providing
desired daylight and contributing significant LEED points in
various categories.
Approvals and certifications for Manchester, N.H.-based Kalwall
Corp.'s translucent curtainwalls may include the latest FM Approval
standard 4881, Class 1 Exterior Walls Systems. This updated
standard addresses the natural hazards to which exterior walls are
commonly exposed, including wind-load rating, windborne-debris
resistance and hail-resistance ratings. To maintain this approval,
curtainwall products must first meet the requirements of Class 1
Fire Rating as identified in Approval Standard 4880. Curtainwall
products designed in accordance with ICC-ES and ASCE 7 methods and
approved to FM 4471 wall and roof system standards-specs covering
high wind, hail and snow loads-are highly desirable, as well.
Kalwall translucent systems can meet hurricane standards ASTM E1886
and E1996, which include the punishing flying debris cannon test
promulgated originally in the Florida Building Code. Curtainwall
products also should pass ASTM E331 for water penetration, ASTM
E283-91 for air leakage and ASTM E330-90 for structural performance
tests. Threats from the ground, such as earthquakes, are just as
dangerous and call for products uniquely engineered to withstand a
building's shaking, twisting, and distortion during temblors and
aftershocks.
On Guard
FM Explosion Venting Walls standard 4440 requires that, should an
explosion occur, dynamic pressures with the potential to collapse a
structure- any increase of internal pressure above 0.29 psi-are
automatically vented. But as with the hurricane standards, the
curtainwall material should remain attached to the structure to
prevent flying debris hazards. Similarly, curtainwall products
should comply with ASTM E1642 and UFC 4-010-01 DoD Minimum
Anti-Terrorism Standards for Buildings; tests for these standards
include applied blast loads from 2 to 6 psi for varying
durations.
Fire tests alone could fill volumes: flame-spread/smoke developed
ratings by UL 723 tunnel tests (including Class A) and listing by
ICC #PFC-1705. Curtainwall products also may need to withstand
extra-high impacts-up to 230 foot-pounds-to protect against
vandalism or other crimes.
Going Green
As the green building movement continues to gain speed, the
environmental consciousness of both a curtainwall product and the
company that makes it becomes increasingly important. Architects
should examine not only how the product contributes to green
building but how it was made-does the manufacturing process reuse
scrap materials, for example?
LEED certification is growing in importance to both architects and
project owners; curtainwall products shown to contribute to LEED
points should receive special attention.
Final
Considerations
Once the numbers are crunched and the certifications considered,
there's a final piece of the puzzle that probably should be first:
aesthetics. Passing every test and gaining every point means little
if the curtainwall product is not flexible enough to allow
architects and designers to realize their visions. Is daylighting
desired, or perhaps even required for a building to achieve its
purpose? Can the product accommodate curves or unusual shapes? Will
it help the project look good, inside and out, both night and
day?
Specifying curtainwall is a complex calculus. The good news is that
thorough research will reveal that of the wide range of products
available today, most are more energy-efficient, environmentally
sound and design friendly than ever before.
Judy Mann is a marketing communications counsel for Manchester,
N.H.-based Mann Inc., an independent firm representing
manufacturers in the field of architectural products. For more
information on Kalwall Corp., visit www.kalwall.com.
www.kalwall.com